1. Field of the Invention
The present invention relates to a polymer-supported constituent for olefin polymerization catalysts, and in particular to a constituent comprising titanium supported on a magnesium-modified chlorine-containing organic polymer, together with an olefin polymerization catalyst containing said polymer-supported constituent and also a process for the polymerization of olefins using such catalysts.
2. Description of the Prior Art
When olefins are polymerized using conventional titanium/organoaluminum catalysts (Ziegler or Ziegler-Natta catalysts), it is necessary to extract the residual catalyst so as to reduce the titanium level in the polymer product below that at which it adversely affects polymer properties, a procedure known as de-ashing. Increasing catalyst activity will result in lower levels of catalyst residue, thereby offering the potential for reducing this residue to a level acceptable in the final product and so eliminating the need for the deashing step. One technique for increasing catalyst activity is to support the titanium on a substrate. Recent developments have yielded highly active catalysts in which the titanium is supported on an active form of magnesium halide, as described in, for example, U.S. Pat. Nos. 4,329,253 and 4,343,721. However, although the increased activity resulting from the use of the magnesium halide support achieves a substantial reduction in titanium residues, the support itself contributes other residues which are not necessarily innocuous. Excessive magnesium content in the polymer can lead to moisture adsorption and to water carryover in film fabrication. Excessive chloride content in the polymer can cause corrosion of fabricating equipment. For these reasons, it would be advantageous to provide a support for a Ziegler catalyst which enhances the activity of the titanium but does not itself contribute residual metals or anions in the polymer product. The use of a polymer support has been disclosed in Japanese Patent Publ. No. 18846/72, which describes a catalyst consisting of (a) a transition metal compound prepared by adhering a halide of magnesium or manganese to the surface of polyolefin or halogenated polyvinyl particles and fixing a titanium or vanadium halide to that coated particle surface, and (b) an organic aluminum or zinc compound. However, the properties of such a catalyst are inevitably critically dependent on the physical characteristics of the polymer particles.